physics, hand holding a chain

[fracturedray]

I'm not seeing a way to utilize the physics with a chain set up and was wondering if there was something I missed.

I built a test arm and at the end/hand I added the physics group and bone to make a sort of chain. It works great if I never move the arm. However if the arm moves around then the physics rotates where the gravity is base off of the arm movement and not base off the original gravity direction. Is there a way to fix this?

Also simply moving the physics group with the chain fails to get any movement like I would get with the Bone Dynamics, seems like a loss, not being able to do that or did I miss something?

I can almost get what I want with the Bone Dynamics however there are some bones under the dynamic bones that I want to move with physics but it won't work.

Think of a swing tied to a tree and it is very windy. So the tree limbs are all moving with bone dynamics but trying to get the swing attached to a limb to use physics and look right is not happening.

My best guess it that it doesn't work this way. If not I have another question. Is there anyway to bake the Bone Dynamics? I know you can do this for the physics but I need it for dynamics.

-ray

[Tagirijus]

Actually I think that I cannot help you at all. Maybe my english is not good enough for understanding your problem 100% (maybe I already have the same problem, hehe).

At least I think that there are 2 features, which are maybe a bit unknown. One feature is the "Use baked physics" (I can find it on the group-layer-settings panel under "Physics"). Maybe this is one thing you have searched for? (A member told me about this feature ini another thread; many other members thanked him )

Another thing I found out is the "Nudge physics" tool. You can find it under the animation menu, I think. I'm not sure at the moment and I am not on the right PC so that I could take a look. Just keep in mind "Nudge physic" or similar. With this tool you can give a physic object in the physic group a "nudge" with a direction and certain power. This way you can nearly move objects by a "ghost hand" even this object should be under the influence of the dynamics!

Hope I could help. Maybe some professionals will answer, too.

Manu

[heyvern]

Physics layers and bones can't be animated. The physics is controlling the animation of layer and bone translation so there would be no way to move that layer. Putting a physics layer inside another layer and moving it also does not create a physics movement. You need to "fake" that type of motion using the other physics tools.

To achieve what you want you need to use the physics to generate the keys you need, then turn off the physics and move or animate those layers to create the effect required.

For a swinging chain from a hand, try the "nudge" physics as mentioned previously or try using motors. A motor can change direction, speed up and slow down, stop etc. You could use that to simulate the swinging hand/arm and then turn off physics and bind the chain layer to the hand bone.

[fracturedray]

Thanks Tagirijus you understood the problem fine.
Thanks heyvern I like the results most from the motor tests.

I did some experiments with y'all suggestions and really liked what I was able to get.

I was looking more at it yesterday and was really wishing I had a way to bake the bone dynamics. So instead, I'll just animate the movement with dynamics on. Then duplicate the layers and use the dynamic movement layer as an onion screen and do the movements by hand so I can fine tune other parts as well.

But before that I'm going to try a few more tests and see if I can get physics close to what I'm getting the dynamics to look like.

Thanks again for the help been reading the tutorials and just never found one for the chain physics. I'll start taking notes and write one about the project I'm doing right now.

[heyvern]

Here's two solutions that could help out.

http://www.lowrestv.com/images/files/ar ... swing.anme

One uses bones the other uses "layer chains".

Bones solution
(First group layer in the sample file)
Top bone is a "pseudo" arm bone. The layer is set to pivot on origin. the top bone of course will be "locked" and rotate on it's base. The layer has a motor that swings causing the motion needed for a hand swinging a chain or string or rope.

You get this how you like and turn off physics and use the generated keys in your animation as needed.

------------------

Layer Chains solution
I love layer chains. Layer chains are chains created from individual layers "linked" together. They use physics to create the chain effect. If the shapes aren't locked properly or the force is to strong they CAN break apart. The advantages are that you can make links heavier by increasing the density of a layer. Also a LARGER shape on a layer AUTOMATICALLY has more density. The physics conforms to the shapes more realistically. Drawback is you can't to do "ropes" or "strings" and set up is a "tad" harder.

You should use my script to split layers. Draw your linked shapes on one layer then split it apart.
viewtopic.php?t=16866

In this version (second group layer in the sample file) I made an "arm layer" as the top "link" holding the "chain". I put a motor on the arm layer similar to the bone layer. Once again, when you have the motion you like you can turn off physics and move/scale this layer where you need it.

None of this is "easy as pie". It takes some brain energy to make it work but it can work. Until a future version of AS has the ability to create physics motion influence from parent layer movement there aren't many other options.

-vern

[fracturedray]

D'oh! I seem to remember reading that quote a while back which means I didn't look very hard to find physics chain tips yesterday. Sorry about that.

I took time to write a very basic "how to" for the chain based off of your help.

Posted here.
viewtopic.php?t=16902

Thanks for the chain swing sample file. It looked better than my tutorial test.

-ray